The study of benzenoid aromatic hydrocarbons and heterocycles has played a crucial role in the understanding of the relationship between pi electron delocalization and molecular stability. In addition, certain benzenoid hydrocarbons and heterocycles are known to be potent carcinogens and this property has been rationalized using molecular orbital theory. This proposal contains a novel and straightforward method of preparing a number of new carbocyclic and heterocyclic nonbenzenoid compounds. Study of these molecules should provide new information concerning the mechanisms by which pi electron conjugation can both stabilize and destabilize cyclic molecules; in addition, a number of such systems having the size, shape and olefinic reactivity presumably necessary for carcinogenic activity will be prepared and made available for physiological testing.